1. Technical Field
This invention relates generally to laser energy removal of thrombi or other obstructions in vessels of the human body, and more particularly to a new and improved method of controlling laser energy during removal to prevent vessel wall damage.
2. Background Information
The possibility of vessel wall damage complicates laser removal of obstructions. Just as laser irradiation can vaporize a targeted lesion, it can damage the untargeted vessel wall. Thus, the physician needs a method of precisely controlling laser delivery.
Advancement of a laser catheter within the vessel up to the lesion may be monitored by cineangiography techniques, and the ablation process monitored by computer analysis of luminescence returning from the lesion, but firing, spotting the effect, and then deciding the next action may nevertheless be somewhat hit-and-miss. The laser beam may miss the target by passing through an existing channel in the lesion or it may break through the lesion, in either case threatening the vessel wall.
In other words, a miss or breakthrough can pass sufficient laser energy beyond the lesion to the vessel wall before detection and cause significant vessel wall damage before aim adjustment or laser deactivation. Consequently, it is desirable to have a new and improved method of laser delivery that overcomes this concern--one adapted to sense a miss or breakthrough as it occurs so that the laser can be deactivated before it damages the vessel wall and the aim readjusted if desired.